<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=Edge,chrome=1">
    <meta name="viewport"
          content="width=device-width, initial-scale=1,minimum-scale=1, maximum-scale=1, user-scalable=no">
    <link rel="shortcut icon" href="img/logo.png">
    <link href="css/style.css" rel="stylesheet" type="text/css"/>
    <title>Title</title>
    <style>
       .a{
           margin: 0 auto;
           width: 100px;
           height:100px;
           background: #007aff;
           display: none;
       }
    </style>
</head>
<body>
<div class="a"></div>
</body>
<script type="text/javascript" src="js/jquery-3.3.1.min.js"></script>
<script>
$(function(){
    $(window).click(function(){
        $('.a').fadeIn("slow");
        fadeOut("slow")
    })
})
</script>
</html>